A single contact zone of the hydrocarbon feedstock with the catalyst is important in a fluid catalytic cracking (FCC) process in order to control the reaction time in the riser. Moreover, a fast mixing of the liquid hydrocarbon feed and the hot regenerated catalysts is desirable to vaporize the feed. The feed nozzle assembly of U.S. Pat. No. 5,306,418 was able to achieve these objectives by having the nozzle assembly inserted from the periphery of the riser reactor, known as side-entry in the industry, and discharging a single sheet-like spray through a single slit opening at the outlet end of the nozzle assembly.
U.S. Pat. No. 5,673,859 described several feed nozzle assembles for similar side-entry applications, one assembly having two converging slits, another having two parallel slits and another having two diverging slits for discharge of a mixture of gas and hydrocarbon liquids. It was described in U.S. Pat. No. 5,673,859 that these nozzle assembles with two discharge slits had the advantage of providing better contacting with catalyst compared to those with a single slit opening, such as U.S. Pat. No. 5,306,418.
U.S. Pat. No. 5,794,857 and U.S. Pat. No. 6,012,652 further described different variations of nozzle assemblies with multiple slit openings at the outlet ends of the nozzle for the side entry application.
U.S. Pat. No. 6,387,247 described a feed nozzle assembly for inserting the nozzle from the bottom of a FCC riser reactor, known as bottom entry in the industry. The spray discharged from such a feed nozzle has the form of a hollow cone. This nozzle cannot achieve a single contact zone of the hydrocarbon feedstock with the catalyst if it is applied to a side entry nozzle configuration because of the discharge being a hollow cone spray.
Although it is commonly understood that the feed nozzle assembly for side entry application with multiple outlet slits, such as U.S. Pat. No. 5,673,859, has the advantage of providing better feed contacting compared to the one with a single outlet slit, such as U.S. Pat. No. 5,306,418, a major disadvantage of the former is that erosion could take place through the gaps in between the multiple slit openings as a result of FCC catalyst particles moving past through these gaps at high velocities, possibly due to a vacuum effect between adjacent sheet like sprays.
One object of the present invention is to create a feed nozzle assembly, which has the advantageous operating properties of a single contact zone with a sheet-like spray. Another objective is to have a feed nozzle assembly providing good feed contacting, such as the nozzle disclosed in for example U.S. Pat. No. 5,794,857 with multiple slits, but is less prone to erosion.